Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. Pacemakers and Implantable Cardiac Defibrillators (ICDs) have proven highly effective in the treatment of a number of cardiac conditions (e.g., arrhythmias). Spinal Cord Stimulation (SCS) systems have long been accepted as a therapeutic modality for the treatment of chronic pain syndromes, and the application of tissue stimulation has begun to expand to additional applications such as angina pectoralis and incontinence. Deep Brain Stimulation (DBS) has also been applied therapeutically for well over a decade for the treatment of refractory chronic pain syndromes, and DBS has also recently been applied in additional areas such as movement disorders and epilepsy. Further, Functional Electrical Stimulation (FES) systems have been applied to restore some functionality to paralyzed extremities in spinal cord injury patients. Furthermore, in recent investigations Peripheral Nerve Stimulation (PNS) systems have demonstrated efficacy in the treatment of chronic pain syndromes and incontinence, and a number of additional applications are currently under investigation. Occipital Nerve Stimulation (ONS), in which leads are implanted in the tissue over the occipital nerves, has shown promise as a treatment for various headaches, including migraine headaches, cluster headaches, and cervicogenic headaches.
These implantable neurostimulation systems typically include one or more electrode carrying stimulation leads, which are implanted at the desired stimulation site, and a neurostimulator (e.g., an implantable pulse generator (IPG)) implanted remotely from the stimulation site, but coupled either directly to the neurostimulation lead(s) or indirectly to the neurostimulation lead(s) via a lead extension. Thus, electrical pulses can be delivered from the neurostimulator to the neurostimulation leads to stimulate the tissue and provide the desired efficacious therapy to the patient. The neurostimulation system may further comprise a handheld patient programmer in the form of a remote control (RC) to remotely instruct the neurostimulator to generate electrical stimulation pulses in accordance with selected stimulation parameters. A typical stimulation parameter set may include the electrodes that are acting as anodes or cathodes, as well as the amplitude, width, and rate of the stimulation pulses.
Thus, the RC can be used to instruct the neurostimulator to generate electrical stimulation pulses in accordance with the selected stimulation parameters. Typically, the stimulation parameters programmed into the neurostimulator can be adjusted by manipulating controls on the RC to modify the electrical stimulation provided by the neurostimulator system to the patient. Thus, in accordance with the stimulation parameters programmed by the RC, electrical pulses can be delivered from the neurostimulator to the stimulation electrode(s) to stimulate or activate a volume of tissue in accordance with a set of stimulation parameters and provide the desired efficacious therapy to the patient. The best stimulus parameter set will typically be one that delivers stimulation energy to the volume of tissue that must be stimulated in order to provide the therapeutic benefit (e.g., treatment of pain), while minimizing the volume of non-target tissue that is stimulated.
The IPG may be programmed by a user, for example, by using a user's programmer (CP), which typically includes a general purpose computer, such as a laptop, with a programming software package installed thereon. Typically, the RC can only control the neurostimulator in a limited manner (e.g., by only selecting a program or adjusting the pulse amplitude or pulse width), whereas the CP can be used to control all of the stimulation parameters, including which electrodes are cathodes or anodes.
The effectiveness of a neurostimulation regimen can best be described in terms of a stimulation capability triad, which includes a spatial component (i.e., stimulating in the right location, which is highly dependent on the disorder to be treated), a temporal component (i.e., stimulating responsive to state, e.g., sensing a relevant physiological parameter and responding with stimulation), and the informational component (i.e., pulsing with patterns to send the right information to stimulate).
With respect to the informational component of the stimulation capability triad, many contemporary neurostimulation systems are programmed with pulse patterns that are either tonic in nature (i.e., a continuous pulse pattern having a uniform pulse rate, pulse width, pulse amplitude, etc. that predictably generates action potentials in the nervous system) or bursted in nature (i.e., a pulse pattern that is alternately turned on and off). However, the human nervous system communicates with the environment using much more sophisticated patterns in which there are encoded many types of information, including pain, pressure, temperature, etc. See Kandel, Schwartz, and Jessell, Principles of Neural Science, 4th edition, which documents how pulse patterns convey information about the size and shape of different types of mechanical stimuli, convey information how about changes in temperature, and convey information about the initiation and cessation of stimuli. Thus, the nervous system can interpret tonic stimulation as an unnatural phenomenon, which may take the form of paresthesia in some neurostimulation applications.
Some contemporary neurostimulation systems, such as auditory/cochlear stimulation and visual/retinal stimulation devices, are programmed to deliver non-tonic pulse patterns that are interpreted by the nervous stimulation as natural or near-natural phenomenon in the form of proper visual or auditory perception. Recently, there has been extensive research in developing the informational component of the stimulation capability triad to improve the efficacy and efficiency of well-known stimulation applications. For example, non-tonic stimulation involving either high pulse rate and/or quick bursting has been shown to avoid potentially uncomfortable side-effects, such as paresthesia, that typically accompany conventional neurostimulation therapy or pain relief. As another example, some stimulation applications attempt to emulate the natural non-tonic signals that the peripheral nervous system naturally senses in response to external stimuli and transmits to the spinal cord, thereby allowing amputees to sense touch, pressure, and temperature via a robotic arm. As still another example, the brain can be stimulated using more energy efficient non-tonic pulse patterns in order to treat Parkinson's Disease.
While a neurostimulation system can be customized to deliver non-tonic pulse patterns that are appropriate for the application to which the neurostimulation system is to be used, such a customized neurostimulation system would be limited to that particular application and generally not usable for applications using different non-tonic pulse patterns. As such, a neurostimulation system that can be dynamically customizable to deliver any non-tonic pulse pattern within safety limits is needed.